Hand-held dispensers, manually-actuatable by a user for operator-controlled discharge of a stored fluid, are widely known in numerous structural configurations and for use with a wide variety of fluids, particularly liquids. In some such dispensers, the operating mechanism is in the nature of a mechanically-driven pump wherein a discharge of stored or contained fluid is effected, by way of example, through hydraulic action, as by temporarily reducing the interior volume of the dispenser to increase the pressure within the dispenser housing and thereby forcibly discharge stored fluid therefrom. Thus, in response to user-selected inward depression or deformation of a part of or element on the dispenser housing, a controllable or predetermined quantity of stored fluid may be ejected through a discharge opening of the dispenser for application to a workpiece. One example of such a dispenser is disclosed in U.S. Pat. No. 4,874,117 of Oct. 17, 1989 to Kay et al.
One problem in dispensers of this type is that, during periods of nonuse of the dispenser, it is all to easy, and not uncommon, for a user or mere handler of the device to inadvertently depress the actuating part of the dispenser and thereby effect an unintended discharge of fluid therefrom. This may result in staining or other damage to clothing and the like or, at the very least, to an unsightly and inconvenient mess and unavoidable embarassment. Even where an associated closure cap is disposed about the discharge end or outlet of the dispenser, one or repeated discharges of fluid into the cap interior are likely to interfere with subsequent operation of the dispenser and to effect sufficient damage to the cap and/or the dispenser outlet region as to seriously reduce the further utility of the dispenser.
The prior art proposes various mechanisms or arrangements seeking to avoid such inadvertent actuation of a fluid dispenser during periods of nonuse. In the aforementioned Kay patent, for example, user-effected inwardly-directed displacement of the actuating button, by which a discharge of fluid is initiated, is prevented, when an associated closure cap is disposed on the dispenser housing, by way of a housing tab or finger that is driven under the button when the cap is seated on the dispenser. Locking mechanisms of this type, however, are subject to eventual failure through material fatigue or failure or distortion should inward force or pressure be repeatedly applied to the actuating button during periods when the button is locked. Once the button is inwardly displaceable, by even a small amount, other internally-disposed actuating members through which the discharge opening is unsealed and a discharge of fluid is driven may be operated whereby an unintended and undesired discharge of stored fluid takes place. Moreover, even in the absence of inward movement of the positionally-locked, user-driven actuating button or the like, those internal dispenser parts through which the discharge outlet is operatively unsealed remain movable or displaceable and are therefore capable of permitting an unintended release of stored fluid from the dispenser interior.